Performance of Varieties under Different Sowing Dates in Soybean (Glycine max L.)

The field experiment was conducted in field at Regional Research Center, Amravati during kharif season 2018-19. Four soybean varieties MACS 1520, AMS MB 5-18, RSC 10-52, and check NRC 86 were sown on two sowing dates, 21 st june (normal sowing) and 10 th july (20 days after normal sowing). The experiment was laid out in split plot design replicated three times keeping sowing dates in main plot and varieties in sub plot using net plot size of 5.0 m x 2.7 m. The observation on dry matter was recorded at 30 DAS, 45 DAS and 60 DAS, CGR and RGR on 30-45 and 45-60 DAS. Yield attributes viz., branches per plant, pods per plant, seed index and seed yield kg/ha and straw yield kg/ha was recorded at the time of harvesting. Amongst the different date of sowing, genotype AMS MB 5-18 recorded significantly highest seed yield 1904 kg/ha under normal date of sowing. In different genotypes, none of the single genotypes proves significantly superior over others. In respect of late sowing genotype, almost all the genotypes recorded less than half seed yield than normal date of sowing.


INTRODUCTION
Soybean has emerged as one of the major oilseed crop and revolutionized rural economy and lifted the socio economic status of soybean farmers. However, the increase in the productivity over the years did follow the same place, and it is not more than half of the world average, hence there is tremendous scope to increase soybean production by enhancing productivity. There are many factors limiting soybean production at farm. These factors are improper sowing time, climatic variability, low germination percentage, poor quality seed, irrigation shortage etc. Another possible reason of low production is the non-adoption of new developed varieties. The sowing of soybean varieties of high yield potential at optimum sowing time is considered as a hopeful approach to increase soybean production. Generally, the sowing dates vary depending on the climatic condition of the region and the varieties to be grown. Different varieties of soybean are sensitive to change in environmental conditions where the crop is being sown.
Therefore, it is also necessary to study the genotype × environment interaction to identify the varieties which are stable in different environments (Calvino et al., 2003a). Sowing dates influence soybean growth stages, due to variation in photoperiod (Han et al., 2006;Kumudini et al., 2007), air temperature (Chen & Wiatrak, 2010), and rainfall distribution and amount during the crop cycle (Hu & Wiatrak, 2012). Meotti et al. (2012) observed that 77 % of soybean yield variability was associated with the climate conditions induced by the sowing dates. Sowing date is the variable with the largest effect on crop yield (Calvino et al., 2003b). Environmental conditions associated with late sowing affect crop features related to the capture of radiation and portioning of crop resources as soybean is a dicotyledonous photoperiod sensitive crop (short day) and faces thermo-sensitivity in nature. These include less vegetative growth (Board et al., 1992), shorter stems (Boquet, 1990); lower reproductive nodes and shortening of the reproductive phases (Kantolic & Slafer, 2001). Delayed sowing generally shifts reproductive growth into less favourable conditions with shorter days and lower radiation and temperature (Egli & Bruening, 2000). In vidarbha region, from last three years the productivity of soybean is consistently decreasing due to unfavorable climatic condition. The other reason behind that the near about 85% farmers are cultivated same genotype year after year i.e. JS-335. Due to increasing in pest and diseases problem and unfavorable climate, JS-335 genotype could not sustain the higher productivity. Now there is need to change/replace the variety which can perform better than existing in respect of adverse climatic condition and productivity Therefore, the present investigation was undertaken to study the performance of different genotype under different sowing dates.

MATERIALS AND METHODS
The field experiment was conducted in field at Regional Research Center, Amravati during kharif season 2018-19. Four soybean varieties MACS 1520, AMS MB 5-18, RSC 10-52, and check NRC 86 were sown on two sowing dates, 21 st june (normal sowing) and 10 th july (20 days after normal sowing). The experiment was laid out in split plot design replicated three times keeping sowing dates in main plot and varieties in sub plot using net plot size of 5.0 m x 2.7 m.
Soil type was medium black with 4.89 kg/ha organic carbon and initial status of soil was 210, 18, 345 Kg/ha NPK respectively. After seed bed preparation, sowing Soybean entries was done by dibbling. The observation on dry matter was recorded at 30 DAS, 45 DAS and 60 DAS, CGR and RGR on 30-45 and 45-60 DAS. Yield attributes viz., branches per plant, pods per plant, seed index and seed yield kg/ha and straw yield kg/ha was recorded at the time of harvesting. Five plants from each net plot were randomly selected and labeled for taking biometric observations at different growth stages. The same plants were harvested separately for post harvest studies. The plants from each net plot were threshed and seeds were cleaned. The cleaned seeds obtained from each net plot were weighted in kg. After separation of seeds from biological yield, remaining material (stem + pod husk) was considered as straw yield and its final weights were recorded in kg per net plot, which were then converted into straw yield (Kg/ha) by multiplying hectare factor.

RESULTS AND DISCUSSION Effect of Sowing Date
The data from table1 revealed that, significantly highest number of branches per plant (2.27), number of pods per plant (52.92), dry weight per plant at 30, 45 and 60 DAS 1.75, 5.34 and 7.08 g respectively were recorded at normal date of sowing. The pods per plant and dry weight per plant in soybean have also been reported to differ in different sowing dates (Nath et al., 2017). The highest CGR at 30-45 DAS & RGR at 45-60 DAS was observed at normal date of sowing and decline later on. Similar reduction in CGR and RGR with delayed sowing of soybean was found by Aastha et al. (2017) and Jagtap et al., (2018). Significantly highest straw yield (2192 kg/ha) was recorded in early date of sowing. Straw yield was an augmenting effect of increased vegetative growth through plant height, number of branches and number of leaves per plant. Profound effect on straw yield per ha. was noted due to different dates of sowing (Jagtap et al., 2018). , Significantly highest grain production efficiency (17.51 kg/ha/day) and rain use efficiency (2.90 kg/hamm) were recorded under normal date of sowing but highest harvest index was observed in late sowing.
From table 3 reveals that, amongst the different date of sowing, genotype AMS MB 5-18 recorded significantly highest seed yield 1904 kg/ha under normal date of sowing. In different genotypes, none of the single genotypes proves significantly superior over others. In respect of late sowing genotype, almost all the genotypes recorded less than half seed yield than normal date of sowing. Shegro et al. (2010) and Shah et al. (2017) also reported the decrease in seed yield with delay in sowing period.

Effect of Varieties
Among different genotypes, significantly highest number of branches was recorded in MACS 1520 & check NRC 86 i.e. 2.27, but found at par with RSC 10-52. In respect of number of pods per plant, significantly highest number of pods was noticed in AMS MB 5-18 i.e. 52.00. Regarding seed test weight, there were no significant difference was observed. Significantly highest dry weight at 30 DAS was recorded in genotype MACS 1520 (1.93 g). At lateral growth stages, there is no significant difference was observed. Highest RGR at 30-45 DAS was recorded in genotype RSC 1052. While amongst the genotypes, significantly highest straw yield (1688 kg/ha), grain production efficiency (13.56 kg/ha/day) and rain use efficiency (2.25 kg/ha-mm) were recorded in AMS MB 5-18. Maximum harvest index 45.61% was observed in MACS 1520 (Table 2). Significantly highest seed yield was found in genotype AMS MB 5-18 (781 kg/ha) while significantly lowest yield was observed i.e. 657 kg/ha in check variety.